The free mobile app, made with Dutch developer Babak Fakhamzadeh with content in Portuguese and English, was released for Android and iOS on Google Play and the App Store. It has location-based content that’s revealed by moving through the port. The area’s role as the largest slave port in the Americas — where hundreds of thousands of enslaved Africans were brought until slavery was abolished in 1889 — is among the 170 stories in the Museum of Yesterday. Users can choose different routes, such as the Terror Tour, Samba Tour, and Corruption Tour, each with its own secrets to unlock.

As a user strolls the streets, they may see the landing of the royal Portuguese family in 1808, or the military coup of 1964 that overthrew President João Goulart, illustrated for the app by artist Juliana Russo and narrated by Anelis Assumpção. Russo also made hand-drawn maps of the contemporary and 1830 versions of the port, allowing users to navigate between centuries, and Assumpção’s narration includes the 19th-century slave announcements published in Rio’s newspapers.

Natalia Viana, Agência Pública director and founder of the app, explained that although they have published articles on slavery past, this was aimed at engaging people with those narratives in new contexts. “We wanted to find a way that this same content, which results from investigations and research, reached different publics,” she told Hyperallergic “This is why, by mixing journalism, urban exploration, and Pokémon GO, we were able to reach tourists, students, and young people who often go to the Port but have no idea how many stories from the past are hidden there.”

That area is in a major time of change (catalyzed by the recent Olympics construction), and there is a concern that with redevelopment, the more uncomfortable parts of the past will be overlooked. The name of the app is a counter to the nearby Museum of Tomorrow, a flashy institution designed by architect Santiago Calatrava that focuses on the future. Viana added that they’re organizing two partnerships to make the app more available, including the Federal University of the State of Rio (UFF), to develop a workshop for college professors to use the app with their students, as well as the tourism agency Redescobrindo o Brasil, which already hosts tours in the city.

And, if you aren’t in Rio, the app can be used anywhere, as long as you’re moving. As Viana stated, “If you download the app, you will be able to do a ‘virtual tour,’ therefore you can access some of the content, in English, by simply walking wherever you are.”